1) Field of the Invention
The present invention relates to a navigation apparatus that performs a route guidance based on preset route information and current position information with an improved guiding effect for a driver.
2) Description of the Related Art
Conventionally, a navigation apparatus, which registers a planned route of its own vehicle and performs route guidance by voice, has been realized. This navigation apparatus specifies a crossing where its own vehicle turns to the right or the left based on planned route information, map information, and a present location and notifies a driver of the crossing in advance to thereby cause the driver to drive according to a set route.
In this case, both screen display and a voice output are used for the notification to the driver. However, since it is not preferable to cause the driver to keep his/her eyes fixed on a display while the driver drives a vehicle, notification by voice is extremely useful. Thus, in the navigation apparatus, it has been an important problem how to increase an amount of information in a voice output and realize effective route guidance without imposing a burden on vehicle operation by the driver.
Therefore, for example, in Japanese Patent Application Laid-Open Publication No. H7-57190, a navigation apparatus performs control such that a guide voice from the navigation apparatus is heard from a relative angle direction with respect to a driver to thereby use a direction of the voice as information. Similarly, Japanese Patent Application Laid-Open Publication No. H6-176296 discloses a technology for localizing an acoustic image in a direction of road guidance to output voice data. Japanese Patent Application Laid-Open Publication No. H8-110237 discloses a technology for changing a localization direction of notification sound according to a state of a route to perform route guidance.
Moreover, in recent years, there has been a development of a navigation apparatus that performs acoustic image localization control for moving an acoustic image of voice guidance urging a user to operate a vehicle in a guiding direction (i.e., sense of movement control (sense of direction control) giving a driver a sense of movement in the guiding direction) according to a behavior of its own vehicle estimated from the guiding direction based on preset route information and position information of its own vehicle.
However, when a direction of a voice output is localized in a guiding direction as in the conventional technologies described above, a driver may be confused if the driver is guided to different directions continuously. For example, when the navigation apparatus guides the driver with a voice “turn to the right at the next crossing and turn to the left at a traffic light ahead”, the voice is outputted from the right direction and, immediately after this, the voice is outputted from the left side. Thus, the driver is conscious of information on the left direction that is heard later. In other words, although it is possible to recognize information by a sentence (contents of a voice) on the driver side as information in time series, it is difficult to recognize information on a direction of sound in time series because later information denies earlier information. Thus, a complicated change in a voice direction requires the driver a labor of “memorizing an order of directions from which sound is heard”.
In addition, in particular, when a guiding direction is the rear or is the left or the right on a rear side, that is, guidance in which a curvature changes largely is performed, if a guide voice is outputted from the rear side, guidance is performed from a direction in which a voice is hard to hear for human ears. Thus, it is likely that the driver misses the guidance. Moreover, even if a route has a large curvature, in actual driving, the navigation apparatus gradually changes a traveling direction of its own vehicle to finally adjust an orientation of its own vehicle to a desired direction. A voice output from a direction opposed to the traveling direction of the own vehicle or a direction near the direction is divergent from a behavior of the own vehicle.
In short, in the conventional technologies described above, there is a problem in that, when an amount of information of a voice output is increased, easiness of listening on a driver side is not taken into account and information divergent from an actual behavior of a vehicle may be added. Thus, it is a conventional problem to increase an amount of information in a voice output without imposing a burden on a driver to thereby improve an effect of route guidance.
In addition, the conventional technologies described above simply perform acoustic image localization control for uniformly moving acoustic images of voice guidance. Thus, there is a problem in that an appropriate sense of movement is not always given to a driver and there is naturally a limit in performing effective route guidance.
For example, in the conventional technologies described above, if acoustic image localization control for moving an acoustic image of relatively short voice guidance of “to the right direction ahead” is performed based on moving speed of an acoustic image at the time when voice guidance of “to the right direction at a crossing ahead”, a voice output of the voice guidance ends before the movement of the acoustic image converges. Thus, it is impossible to give a driver an appropriate sense of movement. In addition, if acoustic image localization control for moving an acoustic image of relatively long voice guidance of “to the right direction at a first traffic signal ahead” is performed, a sense of incompatibility is caused in that, although movement of the acoustic image converges, the voice guidance continues to be outputted.
In general, since a seating position of a driver is on the right side (or the left side) of a vehicle rather than the center of the vehicle, a space in which an acoustic image can be moved in front of the driver is asymmetrical. Therefore, when route guidance to a direction of a seat of the driver (e.g., the right direction) is performed, as usual, even if it is attempted to move an acoustic image of voice guidance in the right direction from the front of the driver, since the right side of the driver is near a door or a window, a moving distance of the acoustic image is limited. Thus, it is difficult to transmit a sense of movement in the guiding direction (right direction) effectively.
Consequently, in addition to transmitting information according to contents meant by voice, it is an extremely important problem how to realize “sense of movement control” excellent in information transmission according to acoustic image movement, that is, how to clearly transmit a sense of movement in a guiding direction to a driver.